Resolution of say 1080 x 720 means 1080 vertical lines of pixels and 720 horizontal line of pixels. This means a total of 777,600 numbers of pixels across the width and breadth of the screen. Now for Spatial resolution say for a 100ppi(considering 100 vertical lines per horizontal 1 inch, if I am correct) the width of the screen comes out to be 1080/100 = 10.8inches. But then how come we have TV screens much larger in size. Does that mean the aspect ratio of say a 30inches(width) TV screen has spatial resolution of just 1080/30 = 36ppi. Then how come the images are of such good quality.

In a phone also we find resolution of 1920 x 1080 then does it mean spatial resolution of the phone will always be better than that of equal resolution TV Screen, which is not apparent. What am I missing here?


closed as off-topic by Leon Heller, Majenko, Andy aka, Rev1.0, Daniel Grillo Jun 16 '14 at 11:17

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – Leon Heller, Majenko, Rev1.0, Daniel Grillo
If this question can be reworded to fit the rules in the help center, please edit the question.

  • 2
    \$\begingroup\$ If you held your phone in front of you at a comfortable position and sat in your armchair to watch the TV, the screen on your phone would look about the same size as the TV screen. \$\endgroup\$ – Andy aka Jun 16 '14 at 9:14

This is really the wrong site for this kind of question. You really should have asked it somewhere like https://physics.stackexchange.com/ (they even have an "optics tag"!)

The images aren't any better quality then the images shown on the phone.

The thing you're missing here is the angular resolution.

Basically, if you look at a phone screen from 10 feet away, you will not be able to make out the image to any significant extent. However, you generally view phones from distances < a few feet. As such, for a pixel to have an angular size where it approaches the resolving power of the human eye, the pixel has to be considerably smaller.

The inverse is true for TVs. If you have a TV with a hypothetical 300 PPI, at normal viewing distances, you will not be able to meaningfully resolve the additional pixels to any great extent.

For various screen sizes (roughly):

  • a 40 inch 1920x1080 HDTV exceeds your eye's ability to resolve discrete pixels when viewed from 5.2 feet or more
  • a 50 inch 1920x1080 HDTV exceeds your eye's ability to resolve discrete pixels when viewed from 6.5 feet or more
  • a 60 inch 1920x1080 HDTV exceeds your eye's ability to resolve discrete pixels when viewed from 7.8 feet or more

Relevant: http://en.wikipedia.org/wiki/Optimum_HDTV_viewing_distance#Human_visual_system_limitation

  • \$\begingroup\$ You mean to say that a 40 inch tv will also have 1920 numbers of horizontal line and so will a 60inch TV screen and a 6inch mobile screen! \$\endgroup\$ – sk1 Jun 16 '14 at 7:55
  • \$\begingroup\$ @sk1 - Uh, yeah, they're all the same resolution. 1920*1080 is 1920*1080 is 1920*1080. Did you think TVs were a different resolution or something? \$\endgroup\$ – Connor Wolf Jun 16 '14 at 7:56
  • 2
    \$\begingroup\$ The critical thing is they all have pixels of roughly the same apparent size, despite having pixels of dramatically different physical size. Things look smaller when you are further away. \$\endgroup\$ – Connor Wolf Jun 16 '14 at 7:58
  • \$\begingroup\$ Can screens with same dimensions and same resolution have different spatial resolutions(in ppi)? \$\endgroup\$ – sk1 Jun 16 '14 at 8:00
  • \$\begingroup\$ @sk1 - The spatial resolution is a function of the physical resolution and the distance it is viewed from, so yes. \$\endgroup\$ – Connor Wolf Jun 16 '14 at 8:01

It's a bit like this: -

enter image description here

On the left my eyes see a phone screen and then, when I look to the right I see a TV screen with the same resolution. They look pretty much the same because they have the same number of pixels per inch.


I think this instructional video explains very clearly the differences between the spatial resolution and physical resolution, just replace the word "cow" with the word "pixel":



Not the answer you're looking for? Browse other questions tagged or ask your own question.